1. Field of the Invention
This invention relates to a method of manufacturing a guidewire with an extrusion jacket, and more particularly, to a method of manufacturing a discrete length guidewire of varying thickness. The invention also relates to a method of manufacturing a discrete length guidewire with a helical stripe on the extrusion jacket.
2. Description of the Related Art
Medical guidewires are generally used for navigating through internal passageways of a body. A typical guidewire includes a corewire having a proximal shaft of constant diameter and a taper section of progressively narrowing diameter leading to a distal tip. In order to prevent damage to the body, the guidewire typically includes a relatively soft plastic jacket on the outer surface. The distal end of a guidewire is introduced into a body by a physician through an opening in the body. The physician manipulates the tip of the guidewire through the body to a site to be treated. A catheter or other medical device is usually advanced over the guidewire to the treatment site, and the guidewire is then removed.
Current methods of manufacturing a guidewire with an extrusion jacket have certain drawbacks. Current methods utilize a continuous spool of corewire during the tapering of sections into the corewire, as well as during the extrusion of a plastic jacket onto the corewire. The use of a continuous spool of corewire during tapering and for extruding a jacket onto the corewire is complex and cumbersome. It is difficult to grind a continuous spool of corewire with a varying tapered diameter.
One method of producing a spool of continuous corewires involves the use of acid to etch a taper onto the corewire. The etching method, however, raises environmental concerns. Therefore, for the above reasons, the current methods for manufacturing a continuous tapered corewire are less than desirable.
After the continuous spool of corewire is manufactured and ground, a plastic jacket is typically applied to the outside surface of the corewire. The current methods utilized in applying a plastic jacket to a continuous spool of corewire have certain drawbacks. A typical method of jacketing a continuous corewire also uses a pay-off spool and take-up spool. In this method, the corewire unwinds from a pay-off spool and is then led through a crosshead with a jacket extruder. As the corewire passes through the crosshead, a jacket is extruded onto the corewire. The jacket is then cooled, and the wire is either respooled onto a take-up spool or cut to a predetermined length. After the corewire is cooled, therefore, additional steps, such as cutting the corewire to a length, are required in order to obtain a usable discrete length guidewire. There is a need therefore for a method of extruding a jacket on a corewire which substantially obviates these drawbacks.
Some jackets of conventional guidewires include a helical stripe to make it easier for a surgeon to see that the guidewire is being longitudinally displaced in the opening of the human body. The current method for applying a jacket having a helical stripe to a corewire also has certain drawbacks. In order to obtain a guidewire with a helical stripe, a heat shrinkable hollow tube is used. The heat shrinkable tubing is manufactured by extruding a longitudinal stripe on the hollow tube and then heating, twisting, and cooling the hollow tube. This heat shrinkable tubing can then be heat shrunk onto a corewire to form the jacket of the corewire. This process of heat shrinking the tubing on a corewire, however, does not provide a very strong connection between the jacket and the corewire. Therefore, this can result in a guidewire in which undesired movement occurs between the corewire and the jacket. Moreover, only a limited number of materials are suitable for heat shrinkable tubing, thereby limiting the type of materials that can be used for the jacket. There is a need therefore for a method of manufacturing a guidewire with a jacket having a helical stripe which substantially obviates these problems.
The advantages and purposes of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages and purposes of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
To attain the advantages and in accordance with the purposes of the invention, as embodied and broadly described herein, the invention includes a method of manufacturing a guidewire having a discrete length. The method includes the steps of: feeding a first end of a corewire into an extrusion device; gripping the first end of the corewire with a gripping apparatus; and extruding a first extrusion material onto an outer surface of the corewire while the gripping apparatus pulls the corewire through the extrusion device to form an extrusion jacket on the outer surface of the corewire. The corewire has a predetermined length corresponding to a length of the guidewire.
In another aspect, the invention includes the above method and the additional step of extruding a visually distinct second extrusion material on the jacket of the corewire while the gripping apparatus pulls the corewire through the extrusion device. During the step of extruding the second extrusion material, the above method further, includes the step of rotating the gripping apparatus to rotate the corewire so that the second extrusion material forms a helical stripe on the jacket of the corewire.
In a further aspect of the invention, the invention includes a corewire to be used in manufacturing a guidewire. The corewire includes: a first end section of a substantially constant diameter; a tip section having a diameter less than the first end section diameter; and a second end section of a substantially constant diameter, the second end section diameter being greater than the diameter of the tip section.
In a yet further aspect of the invention, the invention includes an apparatus for manufacturing a discrete length guidewire having an extrusion jacket. The apparatus includes: a first extruder for supplying a first extrusion material onto an outer surface of a corewire to form an extrusion jacket; and a gripping apparatus for gripping a portion of the corewire that has passed through the first extruder, the gripping apparatus being capable of imparting a motion on the corewire as the corewire passes through the first extruder The gripping apparatus is capable of varied movement to change a physical characteristic of the extrusion jacket.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.